This invention relates to hydrostatic steer controls and more particularly to rotary valve structures for such hydrostatic controls.
It is desirable in transmissions for steer-by-driving vehicles to design the steer control so that the operator uses one maneuver for a right turn and an opposite maneuver for a left turn, whether the vehicle is driving in forward or reverse. An example of a steer-by-driving transmission is shown in U.S. Pat. No. 4,614,131 issued to Hall III, Sept. 30, 1986. Prior art devices for providing similar steer control such as that shown in U.S. Pat. No. 3,717,212 to Potter, issued Feb. 20, 1973, use two distinct servo valve assemblies. One servo valve assembly controls turning during forward operation and the other controls steering during reverse operation. In Potter, the valve members are interconnected by linkages which, of course, require considerable space to accommodate the mechanical components.